1. Field of the Invention
This invention pertains to a method of producing concrete. More particularly, it relates to a method which comprises the primary mixing step for preparing mortar by mixing cement, fine aggregates and water and the secondary mixing step for mixing the mortar and coarse aggregates to produce concrete, and which can produce concrete having an excellent slump value and a high degree of strength, while reducing the unit quantity of water required for obtaining the desired consistency.
2. Description of the Prior Art
Concrete shrinks with the evaporation of water during its solidification. The more water it contains, the more heavily it shrinks and the more likely it is to crack and lower its durability.
U.S. Pat. No. 4,403,863 discloses a method of producing concrete by a stationary mixer including an upper mixer which prepare mortar by mixing cement, fine aggregates and water and a lower mixer which receives the mortar from the upper mixer and mixes it with coarse aggregates. This method may be able to achieve some reduction in the quantity of water required for producing concrete, but is not expected to produce concrete which is satisfactory in slump value and compressive strength, since cement begins to solidify in the lower mixer.